Processing of magnetically recorded data to detect fraud

ABSTRACT

A coil (6) forming part of a tuned circuit (8) is wound around a gapped magnetic core (2). As a magnetic stripe (14) is passed under core (2), variations to the amplitude and frequency of the circuit (8) occur dependent upon the magnetic data on the strip (14). Selected data are manipulated to derive several values (32, 36, 38, and 40) for combination via AND-gate (47). Only if the combination value is above a threshold value is an indication given that the stripe (14) is genuine and not an attempted copy.

The present invention relates to a method of, and apparatus for, readingmagnetically encoded information, the apparatus comprising:

a gapped magnetic core;

a coil wound upon the core and forming part of a tuned circuit;

an oscillator for driving the tuned circuit at a frequency lying on itsresonance curve;

means for providing a first signal dependant upon the amplitude ofsignals occuring within the tuned circuit; and

verification means for verifying the genuineness of the magneticallyencoded information, which verification means comprises means forproviding a second signal dependant upon the frequency of signalsoccurring within the tuned circuit.

Substrates beating magnetically encoded information are increasinglybeing used, for example, in point-of-sale or automated transactionapplications.

A known apparatus of the above general kind is described in ourpublished UK patent number GB 2,035,659. In this apparatus the gappedcore and associated coil are held just above and pass over a magneticstripe. The magnetic stripe comprises alternate sections of permanentlyaligned ferrous oxide particles interspersed with sections of eitherdifferently aligned or randomly oriented ferrous oxide particles. Thechanges in magnetic permeability of the stripe in the different sectionsas the core passes over it induce variations in the frequency of theresonant circuit. A signal dependent on this frequency is used todetermine whether the stripe under examination is genuine or not.

Whilst the known apparatus operates in an entirely satisfactory manner,a system which offers improved discrimination performance over the priorart is an attractive proposition because of the more widespread use ofsubstrates bearing such magnetically encoded information.

According to one aspect of the present invention an apparatus as definedin the first paragraph is characterized in that in that the verificationmeans further comprises:

means for deriving from the first and second signals a plurality ofoutput values representative of signal amplitude and frequencyvariations occurring within the circuit upon relative movement betweenthe coil and the magnetically encoded information;

means for comparing at least one of the output values representative ofsignal amplitude variations and at least one of the output valuesrepresentative of signal frequency variations, or functions thereof,with either other output values or known reference values, thereby toobtain a plurality of test values derived from the comparison; and

means for combining the test values to provide a combination value, suchthat a positive indication of genuine magnetically encoded informationis obtained in dependence upon the combination value having a definedrelationship with a predetermined threshold value.

Hence by provision of several test values, all of which must possesscertain minimum or maximum requirements, a potentially more securediscrimination system as between genuine and attempted copies ofmagnetically encoded information than has hitherto been available isprovided.

The present invention, in another aspect, provides a method of readingmagnetically encoded information including: passing the magneticallyencoded information by a gapped magnetic core which has a coil woundthereupon, the coil forming part of a tuned circuit driven at theresonant frequency by an oscillator; and providing a first signaldependent upon the amplitude of signals occurring within the tunedcircuit and a second signal dependent upon the frequency of signalsoccurring within the tuned circuit; characterized by deriving from thefirst and second signals a plurality of output values representative ofsignal amplitude and frequency variations produced within the circuit bythe passing; comparing at least one of the output values representativeof signal amplitude variations and at least one of the output valuesrepresentative of signal frequency variations, or functions thereof,with either other output values or known reference values, therebyobtaining a plurality of test values; and, combining the test values toprovide a combination value, such that a positive indication of genuinemagnetically encoded information is obtained in dependence upon thecombination value having a defined relationship with a predeterminedthreshold value.

The present invention will now be described, by way of example only,with reference to the accompanying drawings, of which;

FIG. 1 shows a representation of a known reader of magnetically encodedinformation;

FIGS. 2(a) and 2(b) illustrate schematically part of an embodiment ofthe present invention;

FIG. 3 illustrates schematically a comparison means employed in thepresent invention; and,

FIGS. 4(a) and 4(b) illustrate graphically the difference detected by anembodiment of the present invention between genuine and attempted copiesof magnetically encoded data.

Referring firstly to FIG. 1, a known reader of magnetically encodedinformation comprises a gapped magnetic core such as ferrite member 2which has gap 4 therein. The ferrite member 2 has a coil 6 woundthereupon, the coil 6 forming part of a tuned circuit 8. The tunedcircuit 8 is driven at its resonant frequency by an oscillator 10.

A card 12 bearing magnetically encoded information, in this example apermanently structured magnetised stripe 14 is introduced to the readerby roller drivers 16 (only one shown) such that the stripe 14 passesbelow and adjacent to the core 2. The gap 4 of the core 2 is aligned sothat the flux lines across it generated by the tuned circuit 8 lie in aknown orientation direction to the direction of the stripe 14.

The resonant frequency of the circuit 8 is chosen to be around 30 khzand as the stripe 14 passes by the core 2, the amplitude and resonantfrequency of the circuit 8 vary because of the changes in magnetic lossand permeability due to the structured regions of stripe 14 influencingthe circuit 8.

It is known that the frequency variations may be used as parameters fordetermining whether the card 12 in question is in fact genuine or anattempted copy. For example, such frequency variations are used todetermine whether or not the stripe 14 is valid and is achieved bydetermining the occurrence of significant changes in the signalfrequency fluctuations.

Referring now also to FIG. 2, it will be seen that the signal amplitudeand frequency variations are used as inputs to buffer and filtercomponents in FIGS. 2(a) and 2(b) respectively.

It will be appreciated that because the circuit components in FIGS. 2(a)and 2(b) operate on their signal inputs in similar fashions, thenreference will only be made to one, 2(a), yet the reference thereto alsoapplies to the operations performed on signal 2(b).

The buffer and filter components 18(a) receive the signal amplitudevariations from the circuit 8. From here, the signal is then split intotwo portions, an upper portion and a lower portion as seen in FIG. 2(a).

The upper portion, as shown in FIG. 2(a), passes via high-pass 20(a) andlowpass 22(a) filters to remove any unwanted noise. The timred signal isthen sent to synchronous detector 26(a) in order to rectify the signalamplitude variations in a known manner. The rectified signal then passeson to an integrator 28(a) to provide amplitude values of the signalamplitude variations. Then a sample-and-hold component 30(a) providesoutput values 32 indicative of the amplitude levels of the signalamplitude variations received by filter and buffer components 18(a) fromthe circuit 8. This upper portion of the signal amplitude variations isobtained when the stripe 14 of the card 12 is moved relative to the gap4 of the core 2, and always being either in contact therewith or spacedby an invariable distance therefrom.

The lower portion of the signal amplitude variations is derived from therelative difference between the amplitude signal when the stripe 14 ofcard 12 is adjacent the gap 4 of the core 12 and when the stripe 14 isaway from the gap 4 so that no magnetic effects are observed. In thislower portion, as shown in the lower split of FIG. 2(a) after the bufferand filter components 18(a), the signal passes via a low-pass filter andtemperature compensation arrangement 24(a) and on to a furthersample-and-hold component 34(a). This then provides an output signal 36indicative of the change in amplitude signal as described above.

Thus signal 32 is indicative of signal amplitude modulations as thestripe 14 passes relative to the gap 4, yet signal 36 is indicative ofthe change in amplitude signal variations when the strip 14 is adjacentthe gap 4 relative to any signal produced at the gap 4 when the stripe14 is not present.

It will be understood that the signal frequency variations in FIG. 2(b)provide frequency modulation values 38 and frequency change values 40 inthe same manner as described above.

The four output values 32,36,38, and 40 are then passed, in the parallelarrangement shown in FIG. 3, to a means for comparing the output values,in this example resistors 42 and comparators 44.

The comparator 44(a) receives both the output value 40 and knownreference voltage 45. The comparator 44(a) will provide a test valueoutput based upon its two inputs. This test value will be high if theoutput value 40 exceeds the value of the reference voltage 45 and low ifnot.

Comparator 44(b) operates in a similar manner to that of comparator44(a), however a test value output which is high is only produced ifoutput value 40 is greater than output value 38.

Comparator 44(c) will produce a high test value if the output value 38coupled with a value dependent upon its associated resistor 42 and addedto the output value 32 is greater than the zero potential value of theother comparator 44(c) input.

Comparator 44(d) operates in a similar fashion to comparator 44(c),except that the two relevant output values under consideration are 38and 36.

Thus the resultant outputs of all comparators 44 are four test values46(a)-(d), each of which is either high or low depending upon the inputsto these comparators.

A means for combining these four test values 46(a)-(d), in this exampleAND-gate 47 receives each such value and provides therefrom acombination value 48. In dependence upon this combination value 48exceeding a present threshold value, then an output from the AND-gate 47provides a positive indication of genuine magnetically encodedinformation. In the current example, if any one of the test values islow, then no such indication is given and the card 12 and stripe 14 arerejected.

Such acceptance/rejection is not an issue germane to the patentabilityof the present invention and so will not be further described herein,although understanding of such is assumed.

FIGS. 4 illustrate the traces seen by comparing a genuine FIG. 4(b),with an attempted copy FIG. 4(a), of stripe 14. The four signalamplitude and frequency modulation and change values, 32,36,38,40respectively are shown in FIGS. 4. The difference between the genuineand attempted copies stripes 14 is thus clearly visible.

Those skilled in the art will appreciate that, whilst in the aboveexample an AND gate 47 exemplifies the means for combining the testvalues, any suitable combination means may be used so long as apredetermined relationship exists between the combination value and thethreshold value. For example, a predetermined threshold may be set suchthat all test values input to the means for combining must be low for apositive output to result, or all test values must be within certainthreshold windows.

It will be apparent that whilst only four test values have beenillustrated in the above example, any number of test values and anysuitable derivation may be employed. For example, the means forcomparing the output values need not simply analyse the output values,per se. Functions or values derived therefrom may also yield usefulcomparison results for providing test values. Examples of such are thesquare or square root of an output value; the division of one outputvalue, or combination of several, by another or others of the outputvalues.

It will be appreciated by those skilled in the art, and particularlywith reference to FIGS. 4 that parity, that is the polarity of thesignals and derived values, is important. if, for example, the polarityof the changes 40,36 were not in the correct sense, then positivediscrimination would not occur. Hence, parity is a furtherdiscriminatory feature of the present invention.

It will be apparent that other criteria may be employed to provideadditional verification parameters to those described hereabove. Forexample, visual identification means or hidden ultra-violet reflectivecodes which may only be seen when illuminated with ultra-violet lightmay also be placed on the card 12 adjacent or on top of the stripe 14.

Those skilled in the art will realise that modifications to the abovemay be made whilst still remaining within the scope of the invention.For example, the temperature compensator included in components 24(a)and (b) may not be required for putting the invention into effect.

It will be apparent also that the concepts of the above invention areequally applicable to the so-called "swipe reader". In such a reader thecard 12 is swiped past the gap 4 of core 2 under manual control withoutthe need for drive rollers 16.

We claim:
 1. Apparatus for reading magnetically encoded information (14)comprising:a gapped magnetic core (2); a coil (6) wound upon the core(2) and forming part of a tuned circuit (8); an oscillator (10) fordriving the tuned circuit (8) at a frequency lying on its resonancecurve; means for providing a first signal dependant upon the amplitudeof signals occurring within the tuned circuit; and verification means(18, 20, 22, 24, 26, 28, 30, 34, 42, 44, 47) for verifying thegenuineness of the magnetically encoded information, which verificationmeans comprises means for providing a second signal dependant upon thefrequency of signals occurring within the tuned circuit, characterizedin that the verification means further comprises: means (18, 20, 22, 24,26, 28, 30, 34) for deriving from the first and second signals aplurality of output values (32, 36, 38, 40) representative of signalamplitude and frequency variations occurring within the circuit (8) uponrelative movement between the coil (6) and the magnetically encodedinformation (14); means (44) for comparing at least one of the outputvalues (32,36) representative of signal amplitude variations and atleast one of the output values (38, 40) representative of signalfrequency variations, or functions thereof, with a value from a groupcomprising the said other output values and functions thereof and knownreference values, thereby to obtain a plurality of test values (46)derived from the comparison; and means (47) for combining the testvalues (46) to provide a combination value (48), such that a positiveindication of genuine magnetically encoded information is obtained independence upon the combination value (48) having a defined relationshipwith a predetermined threshold value.
 2. Apparatus according to claim 1wherein the signal amplitude and frequency variations comprise: offsetsfrom respective amplitude and frequency reference values; and amplitudeand frequency modulations about the offset amplitude and frequencyvalues.
 3. Apparatus according to claim 2 wherein the means for derivinga plurality of output values includes first and second pairs ofcircuits, the first circuit of the first pair having its input coupledto the output of the means for providing a first signal, and the secondcircuit of the first pair having its input coupled to the output of themeans for providing a second signal, each circuit of the first pairincluding a band-pass filter, a rectifier, an integrator and asample-and-hold component beinq connected in series, the first circuitof the second pair having its input coupled to the means for providing afirst signal and the second circuit of the second pair having its inputcoupled to the means for providing a second signal, each circuit of thesecond pair including a low-pass filter and a sample-and-hold componentbeing connected in series.
 4. Apparatus according to claim 1 wherein themeans for comparing the output values comprises a plurality ofcomparators arranged to receive predetermined permutations of thedifferent output values and provide therefore, from each comparator, asingle test value.
 5. Apparatus according to claim 4 wherein thepredetermined permutations of the different output values compriseeither permutations of the output values themselves, or permutations offunctions thereof or mathematically derived therefrom.
 6. Apparatusaccording to claim 1 wherein the means for combining the test valuescomprises an AND-gate.
 7. Apparatus according to claim 1 wherein thedefined relationship is that the combination value is greater than thepredetermined threshold value to indicate a positive genuine,magnetically encoded information.
 8. A method of reading magneticallyencoded information (14) comprising: passing the magnetically encodedinformation (14) by a gapped magnetic core (2) which has a coil (6)wound thereupon, the coil (6) forming part of a tuned circuit (8) drivenat the resonant frequency by an oscillator (10); providing a firstsignal dependent upon the amplitude of signals occurring within thetuned circuit and a second signal dependent upon the frequency ofsignals occurring within the tuned circuit; deriving from the first andsecond signals a plurality of output values (32, 36, 38, 40)representative of signal amplitude and frequency variations producedwithin the circuit (8) by the passing; comparing at least one of theoutput values (32, 36) representative of signal amplitude variations andat least one of the output values (38, 40) representative of signalfrequency variations, or functions thereof, with, a value from a groupcomprising said other output values and functions thereof and knownreference values, thereby obtaining a plurality of test values (46); andcombining the test values (46) to provide a combination value (48), suchthat a positive indication of genuine magnetically encoded informationis obtained in dependence upon the combination value (48) having adefined relationship with a predetermined threshold value.